Crank-case scavenged two-stroke engines are widely used in applications here high power to weight ratios are sought. It is common for crank case scavenged engines to mix lubricating oil with the fuel and to rely upon crank case turbulence during change induction to lubricate the engine bearings.
When multi-cylinder crank case scavenged engines are used for cold weather applications such as snowmobiles, lubrication problems can occur, if particulates are drawn into, and clog, the fuel jets.
It has been found that in cold weather, water within the fuel can condense and freeze within the fuel jet of the carburetor, thus blocking fuel delivery. This blockage can result in a lean mixture. Such lean mixtures cause the affected cylinder to run "hot" and also reduce cylinder wall and bearing lubrication.
This problem is particularly severe in snowmobiles where substantial amount of snow and ice often surround the induction portions of individual cylinders. In multiple cylinder configurations, all cylinders continue to move even if the fuel flow is obstructed to one of the cylinders. This may result in continued operation of the cylinder having a lean mixture results in substantial engine damage.
The prior art recognizes this problem. U.S. Pat. No. 4,793,950 to Hedlund, teaches the use of a flexible rubber collection tube located directly below the fuel jet to collect contaminants.